Sebastien Buemi is officially on reserve duty for the AlphaTauri and Red Bull Formula 1 teams after Sergio Sette Camara was able to enter Japan to race in Super Formula.
Sette Camara has been the reserve for the two Red Bull-owned teams this season, and has been present at races.
The Brazilian was supposed to be combining the reserve role with a Super Formula programme, but COVID-19 travel restrictions meant that he missed the first two races of the delayed season.
Sette Camara was replaced at the B-Max team by Teppei Natori at Motegi, although he withdrew from the race amid dehydration concerns, and by Mitsunori Takaboshi at Okayama.
However, the Brazilian has been able to pick up his Super Formula programme from the third round at Sugo, in which he took a surprise pole position in his first outing for the team - despite having caused two red flags in practice.
Sette Camara lost the lead to Ryo Hirakawa at the start and then suffered a slow pitstop to fall out of podium contention, before he crashed on his out-lap on cold tyres.
The rest of the Super Formula season has two direct clashes with F1, with Autopolis on 15 November overlapping with Turkey, and the twin Suzuka events on 5-6 December with the second Bahrain race.
However with ongoing quarantine rules in Europe, Sette Camara looks set to remain in Japan, which means that Buemi will be on Red Bull duty for the rest of the year.
The Swiss driver, who is entitled to a superlicence as World Endurance champion, has long been part of Red Bull's back-up plans, although Sette Camara had priority this season.
He last raced in F1 with the then Toro Rosso team in 2011. However he has remained up to speed with current machinery with extensive running in the Red Bull simulator, as well as combining racing programmes in Formula E and the WEC.
The plan is that should one of the Red Bull drivers be indisposed either Pierre Gasly or Daniil Kvyat will step up, and the reserve will then take the vacated seat at AlphaTauri.
Autosport has produced a standalone special magazine to celebrate our 70th birthday. All current print subscribers will receive a copy for free. To order your copy of the 196-page Autosport 70th Anniversary issue, please go to: autosport.com/autosport70th